Stroke is a leading cause of death and disability and a growing problem to global healthcare. In the US alone, over 700,000 people per year suffer a major stroke and, of these, over 150,000 people die. Even more disturbing, this already troubling situation is expected to worsen as the “baby boomer” population reaches advanced age, particularly given the number of people suffering from poor diet, obesity and/or other contributing factors leading to stroke. Of those who a survive stroke, approximately 90% will suffer long term impairment of movement, sensation, memory or reasoning, ranging from mild to severe. The total cost to the US healthcare system is estimated to be over $50 billion per year.
Strokes may be caused by a rupture of a cerebral artery (“hemorrhagic stroke”) or a blockage in a cerebral artery due to a thromboembolism (“ischemic stroke”). A thromboembolism is a detached blood clot that travels through the bloodstream and lodges in a manner that obstructs or occludes a blood vessel. Between the two types of strokes, ischemic stroke comprises the larger problem, with over 600,000 people in the US suffering with ischemic stroke per year.
Ischemic stroke treatment may be accomplished via pharmacological elimination of the thromboembolism and/or mechanical elimination of the thromboembolism. Pharmacological elimination may be accomplished via the administration of thrombolytics (e.g., streptokinase, urokinase, tissue plasminogen activator (TPA)) and/or anticoagulant drugs (e.g., heparin, warfarin) designed to dissolve and prevent further growth of the thromboembolism. Pharmacologic treatment is non-invasive and generally effective in dissolving the thromboembolism. Notwithstanding these generally favorable aspects, significant drawbacks exist with the use of pharmacologic treatment. One such drawback is the relatively long amount of time required for the thrombolytics and/or anticoagulants to take effect and restore blood flow. Given the time-critical nature of treating ischemic stroke, any added time is potentially devastating. Another significant drawback is the heightened potential of bleeding or hemorrhaging elsewhere in the body due to the thrombolytics and/or anticoagulants.
Mechanical elimination of thromboembolic material for the treatment of ischemic stroke has been attempted using a variety of catheter-based transluminal interventional techniques. One such interventional technique involves deploying a coil into a thromboembolism (e.g. via corkscrew action) in an effort to ensnare or envelope the thromboembolism so it can be removed from the patient. Although an improvement over pharmacologic treatments for ischemic stroke, such coil-based retrieval systems have only enjoyed modest success (approximately 55%) in overcoming ischemic stroke due to thromboembolic material slipping past or becoming dislodged by the coil. In the latter case, the dislodgement of thromboembolic material may lead to an additional stroke in the same artery or a connecting artery.
Another interventional technique involves deploying a basket or net structure distally (or downstream) from the thromboembolism in an effort to ensnare or envelope the thromboembolism so it can be removed from the patient. Again, although overcoming the drawbacks of pharmacologic treatment, this nonetheless suffers a significant drawback in that the act of manipulating the basket or net structure distally from the occluded segment without angiographic roadmap visualization of the vasculature increases the danger of damaging the vessel. In addition, removing the basket or net structure may permit if not cause thromboembolic material to enter into connecting arteries. As noted above, this may lead to an additional stroke in the connecting artery.
A still further interventional technique for treating ischemic stroke involves advancing a suction catheter to the thromboembolism with the goal of removing it via aspiration (i.e. negative pressure). Although generally safe, removal via aspiration is only effective with relatively soft thrombus-emboli. To augment the effectiveness of aspiration techniques, a rotating blade has been employed to sever or fragment the thromboembolism, which may thereafter be removed via the suction catheter. While this rotating blade feature improves the effectiveness of such an aspiration technique, it nonetheless increases the danger of damaging the vessel due to the rotating blade.
The foregoing interventional techniques, as well as others in the prior art, all suffer one or more drawbacks and are believed to be sub-optimal for treating ischemic stroke. The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art.
When such an obstruction occurs in a cerebral vessel, the result is a stroke and potential cell death soon thereafter. The resulting symptoms of immobility and/or loss of function depend upon the location of the occlusion within the cerebrovasculature, and the severity of impact of ischemic stroke is directly related to the length of time blood flow is occluded in a particular cerebral vessel. Specifically, regardless of the means of complete removal of a thromboembolism, a common urgency remains: to restore blood flow through the vessel as soon as possible after occlusion in order to minimize cell death during the acute phase of stroke, (and/or during the initial treatment of a patient) while physicians determine the desired course of treatment for permanent and complete elimination of the embolism. It is an object of the invention herein to provide a means for temporarily restoring blood flow through a blocked cerebral vessel, prior to and/or during the procedures to more permanently and completely remove the blockage, and to permanently and completely remove the blockage. It is a further object of the invention to remove embolic material from the vessel. It is a further object of the invention to provide a device that can be readily tracked through the tortuous and fragile anatomy of the cerebrovasculature. It is a further object of the invention to provide a device that will load readily into a delivery catheter, will deploy readily within the cerebrovasculature at the site of an occlusion, and will be readily removable via the delivery catheter following restoration of sufficient blood flow. It is a further object of the invention to permit the delivery and deployment of additional therapies (such as, for example, disruption and aspiration of the embolism) during use of the device.
In a first aspect, the present invention provides a system for removing thromboembolic material from a blood vessel. The system includes an elongate catheter proportioned for insertion into a blood vessel, where the catheter has a lumen extending therethrough. An elongate member is mounted to extend and retract through the lumen, and an expandable and collapsible separator element is disposed at a distal end of the elongate member. The separate element comprises a plurality of uprights and a multiplicity of apexes extending between said uprights, wherein at least some of the uprights and a first group of apexes are disposed about a central longitudinal axis of the separator and a second group of the apexes extend inwardly toward the central longitudinal axis of the separator.
In a second aspect, the present invention provides a method of manufacture of a system for removal of thromboembolic material from a blood vessel. The method comprises the steps of cutting a plurality of uprights and apexes from a length of tubing to form a separator element adjoining some of the apexes to one another, and mounting said separator element to an elongate element.
In a third aspect, the present invention provides a method of removal of thromboembolic material from a blood vessel of a subject. The method comprises the steps of introducing into the vessel proximate the thromboembolic material an elongate member having an expandable and collapsible separator element disposed at a distal end of the elongate member. The separator element comprises a plurality of uprights and a multiplicity of apexes extending between said uprights, wherein at least some of the uprights and a first group of apexes are disposed about a central longitudinal axis of the separator and a second group of the apexes extend inwardly toward the central longitudinal axis of the separator.